The present invention relates to transgenic hosts particularly transgenic plants, plant tissues, seeds and cells that are trichothecene resistant and methods of making and using the same. The present invention further relates to methods of preventing and/or reducing fungal growth on a plant, plant tissue, seed or plant cell. The present invention further relates to preventing and/or reducing mycotoxin contamination of a plant, plant tissue or seed. The present invention further relates to using trichothecenes as selective agents in transformation protocols.
Numerous fungi are serious pests of economically important agricultural crops. Further, crop contamination by fungal toxins is a major problem for agriculture throughout the world. Mycotoxins are toxic fungal metabolites, often found in agricultural products that are characterized by their ability to cause health problems for vertebrates. Trichothecenes are sesquiterpene epoxide mycotoxins produced by species of Fusarium, Trichothecium, and Myrothecium that act as potent inhibitors of eukaryotic protein synthesis. Fusarium species that produce such trichothecenes include F. acuminatum, F. crookwellense, F. culmorum, F. equiseti, F. graminearum (Gibberella zeae), F. lateritium, F. poae, F. sambucinum (G. pulicaris), and F. sporotrichioides (Marasas, W. F. O., Nelson, P. E., and Toussoun, T. A. 1984).
As previously described (A. E.Desjardins and T. M Hohn, Mycotoxins in plant pathogenesis.Mol.Plant-Microbe Interact. 10 (2):147-152, 1997), both acute and chronic mycotoxicoses in farm animals and in humans have been associated with consumption of wheat, rye, barley, oats, rice and maize contaminated with Fusarium species that produce trichothecene mycotoxins. Experiments with chemically pure trichothecenes at low dosage levels have reproduced many of the features observed in moldy-grain toxicoses in animals, including anemia and immunosuppression, hemorrage, emesis and feed refusal. Historical and epidemiological data from human populations indicate an association between certain disease epidemics and consumption of grain infected with Fusarium species that produce trichothecenes. In particular, outbreaks of a fatal disease known as alimentary toxic aleukia, which has occurred in Russia since the nineteenth century, have been associated with consumption of over-wintered grains contaminated with Fusarium species that produce the trichothecene T-2 toxin. In Japan, outbreaks of a similar disease called akakabi-byo or red mold disease have been associated with grain infected with Fusarium species that produce the trichothecene, deoxynivalenol (hereinafter xe2x80x9cDONxe2x80x9d). Trichothecenes were detected in the toxic grain samples responsible for recent human disease outbreaks in India and Japan. There exists, therefore, a need for agricultural methods for preventing and, crops having reduced levels of, mycotoxin contamination.
Further, trichothecene-producing Fusarium species are destructive pathogens and attack a wide range of plant species. The acute phytotoxicity of trichothecenes and their occurrence in plant tissues also suggest that these mycotoxins play a role in the pathogenesis of Fusarium on plants. This implies that mycotoxins play a role in disease and, therefore, reducing their toxicity to the plant may also prevent or reduce disease in the plant. Further, reduction in disease levels may have the additional benefit of reducing mycotoxin contamination on the plant and particularly in grain where the plant is a cereal plant.
Various methods of controlling diseases in plants, such as corn ear rot, stock rot or wheat head blight, have been used with varying degrees of success. One method of controlling plant disease has been to apply an antimicrobial chemical to crops. This method has numerous, art-recognized problems. Alternatively, a more recent method involves the use of biological control organisms (xe2x80x9cbiocontrolxe2x80x9d) which are natural competitors or inhibitors of the pest organism. However, it is difficult to apply biocontrol to large areas, and even more difficult to cause those living organisms to remain in the treated area for an extended period of time. More recently, techniques in recombinant DNA have provided the opportunity to insert into plant cells cloned genes, which express antimicrobial compounds. However, this technology has given rise to concerns about eventual microbial resistance to well-known, naturally occurring antimicrobials. Thus, a continuing need exists to identify naturally occurring antimicrobial agents, such as proteins, which can be formed by plant cells directly by translation of a single gene.
A trichothecene 3-O-acetyltransferase that catalyzes the acetylation of a number of different Fusarium trichothecenes including DON at the C3 hydroxyl group has been identified in Fusarium sporotrichioides. (S. P. McCormick, N. J. Alexander, S. C. Trapp, and T. M. Hohn. Disruption of TRI101, the gene encoding trichothecene 3-O-acetyltransferase, from Fusarium sporotrichioides. Applied. Environ. Microbiol. 65 (12):5252-5256, 1999.) Acetylation of trichothecenes at the C3-OH significantly reduces their toxicity in vertebrates and plants and results in the reaction product 3-acetyldeoxynivalenol (hereinafter xe2x80x9c3ADONxe2x80x9d) See, Kimura et al. below.
The sequence of structural genes encoding trichothecene 3-O-acetyl transferases from Fusarium graminearum, Fusarium sporotrichioides as well as sequences of other orthologs has been published. See, e.g. Kimura et al., Biosci. Biotechnol. Biochem., 62 (5) 1033-1036 (1998), and Kimura et al., FEBS Letters, 435, 163-168 (1998). Further, it has been speculated that the gene from Fusarium sporotrichioides encoding a trichothecene 3-O-acetyl transferase may be useful in developing plant varieties with increased resistance to Fusarium. See., e.g. Hohn, T. M. et al. Molecular Genetics of Host-Specific Toxins in Plant Disease, 17-24 (1998), and Kimura et al. J.Biological Chemistry, 273(3) 1654-1661 (1998).
Prior to the present invention, however, many uncertainties rendered it far from obvious whether expressing trichothecene 3-O-acetyl transferases in a plant would actually lead to trichothecene resistant plants. For example, the reaction catalyzed by the Fusarium sporotrichoides trichothecene 3-O-acetyl transferase is reversible and might, therefore have failed to protect plant cells from trichothecenes such as DON. It was also uncertain whether there might be esterases in plant cells that would compete with the 3-O-acetyl transferase activities to generate toxic DON from 3ADON. It was also uncertain how the metabolism of the reaction product 3ADON might affect the plant, e.g. whether introduction of the trichothecene 3-O-acetyltransferase would alter plant growth and development in ways that would negate any positive contribution of the acetyltransferase by for example, interfering with the plant""s natural disease resistance mechanisms. It was also uncertain whether 3ADON could be metabolized by the plant to form a novel secondary metabolite with toxic effects. It was also uncertain, even if DON produced by an invading fungus was efficiently converted to 3ADON, whether this conversion would impart enhanced pathogen resistance upon the plant. The above are but a few of the uncertainties in the art before the time of the present invention.
Expression refers to the transcription and/or translation of an endogenous gene or a transgene in plants. In the case of antisense constructs, for example, expression may refer to the transcription of the antisense DNA only.
Operably linked/associated when referring to a regulatory DNA sequence being xe2x80x9coperably linked toxe2x80x9d or xe2x80x9cassociated withxe2x80x9d a DNA sequence that codes for an RNA or a protein refers to the two sequences being situated such that the regulatory DNA sequence affects expression of the coding DNA sequence.
The term xe2x80x9cheterologous polynucleotidexe2x80x9d or xe2x80x9cheterologous DNAxe2x80x9d as used herein each refers to a nucleic acid molecule not naturally associated with a host cell into which it is introduced, including genetic constructs, non-naturally occurring multiple copies of a naturally occurring nucleic acid molecule; and an otherwise homologous nucleic acid molecule operatively linked to a non-native nucleic acid molecule. Thus, a heterologous gene in a host cell includes a gene that is endogenous to the particular host cell but has been modified through, for example, the use of DNA shuffling. Thus, the terms encompasses a DNA segment that is foreign or heterologous to the cell, or homologous to the cell but in a position within the host cell nucleic acid in which the element is not ordinarily found.
The terms xe2x80x9cnucleic acidxe2x80x9d or xe2x80x9cpolynucleotidexe2x80x9d refers to deoxyribonucleotides or ribonucleotides and polymers thereof in either single- or double-stranded form. Unless specifically limited, the term encompasses nucleic acids containing known analogues of natural nucleotides which have similar binding properties as the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g. degenerate codon substitutions) and complementary sequences and as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions may be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and/or deoxyinosine residues (Batzer et al., Nucleic Acid Res. 19: 5081 (1991); Ohtsuka et al., J. Biol. Chem. 260: 2605-2608 (1985); Rossolini et al., Mol. Cell. Probes 8: 91-98 (1994)). The terms xe2x80x9cnucleic acidxe2x80x9d or xe2x80x9cnucleic acid sequencexe2x80x9d or xe2x80x9cpolynucleotidexe2x80x9d may also be used interchangeably with gene, cDNA, and mRNA encoded by a gene.
In its broadest sense, the term xe2x80x9csubstantially similarxe2x80x9d, when used herein with respect to a nucleic acid molecule, means a nucleic acid molecule corresponding to a reference nucleotide sequence, wherein the corresponding nucleic acid molecule encodes a polypeptide having substantially the same structure and function as the polypeptide encoded by the reference nucleotide sequence, e.g. where only changes in amino acids not affecting the polypeptide function occur. Desirably the substantially similar nucleic acid molecule encodes the polypeptide encoded by the reference nucleotide sequence. The term xe2x80x9csubstantially similarxe2x80x9d is specifically intended to include nucleic acid molecules wherein the sequence has been modified to optimize expression in particular cells, e.g. in plant cells. The percentage of identity between the substantially similar nucleic acid molecule and the reference nucleotide sequence desirably is at least 45%, more desirably at least 65%, more desirably at least 75%, preferably at least 85%, more preferably at least 90%, still more preferably at least 95%, yet still more preferably at least 99%. Preferably, the percentage of identity exists over a region of the sequences that is at least about 50 residues in length, more preferably over a region of at least about 100 residues, and most preferably the sequences are substantially similar over at least about 150 residues. In a most preferred embodiment, the sequences are substantially similar over the entire length of the coding regions. Sequence comparisons may be carried out using a Smith-Waterman sequence alignment algorithm and as described in more detail below (se e.g. Waterman, M. S. Introduction to Computational Biology: Maps, sequences and genomes. Chapman and Hall. London: 1995. ISBN 0-412-99391-0. The local S program, version 1.16, is used with following parameters: match: 1, mismatch penalty: 0.33, open-gap penalty: 2, extended-gap penalty: 2.
Another indication that a nucleic acid sequences is a substantially similar nucleic acid of the invention is that it hybridizes to a nucleic acid molecule of the invention under stringent conditions. The phrase xe2x80x9chybridizing specifically toxe2x80x9d refers to the binding, duplexing, or hybridizing of a molecule only to a particular nucleotide sequence under stringent conditions when that sequence is present in a complex mixture (e.g., total cellular) DNA or RNA. xe2x80x9cBind(s) substantiallyxe2x80x9d refers to complementary hybridization between a probe nucleic acid and a target nucleic acid and embraces minor mismatches that can be accommodated by reducing the stringency of the hybridization media to achieve the desired detection of the target nucleic acid sequence.
xe2x80x9cStringent hybridization conditionsxe2x80x9d and xe2x80x9cstringent hybridization wash conditionsxe2x80x9d in the context of nucleic acid hybridization experiments such as Southern and Northern hybridizations are sequence dependent, and are different under different environmental parameters. Longer sequences hybridize specifically at higher temperatures. An extensive guide to the hybridization of nucleic acids is found in Tijssen (1993) Laboratory Techniques in Biochemistry and Molecular Biology-Hybridization with Nucleic Acid Probes part I chapter 2 xe2x80x9cOverview of principles of hybridization and the strategy of nucleic acid probe assaysxe2x80x9d Elsevier, New York. Generally, highly stringent hybridization and wash conditions are selected to be about 5xc2x0 C. lower than the thermal melting point (Tm) for the specific sequence at a defined ionic strength and pH. Typically, under xe2x80x9cstringent conditionsxe2x80x9d a probe will hybridize to its target subsequence, but to no other sequences.
The Tm is the temperature (under defined ionic strength and pH) at which 50% of the target sequence hybridizes to a perfectly matched probe. Very stringent conditions are selected to be equal to the Tm for a particular probe. An example of stringent hybridization conditions for hybridization of complementary nucleic acids which have more than 100 complementary residues on a filter in a Southern or northern blot is 50% formamide with 1 mg of heparin at 42xc2x0 C., with the hybridization being carried out overnight. An example of highly stringent wash conditions is 0.15M NaCl at 72xc2x0 C. for about 15 minutes. An example of stringent wash conditions is a 0.2xc3x97SSC wash at 65xc2x0 C. for 15 minutes (see, Sambrook, infra, for a description of SSC buffer). Often, a high stringency wash is preceded by a low stringency wash to remove background probe signal. An example medium stringency wash for a duplex of, e.g., more than 100 nucleotides, is 1xc3x97SSC at 45xc2x0 C. for 15 minutes. An example low stringency wash for a duplex of, e.g., more than 100 nucleotides, is 4-6xc3x97SSC at 40xc2x0 C. for 15 minutes. For short probes (e.g., about 10 to 50 nucleotides), stringent conditions typically involve salt concentrations of less than about 1.0 M Na ion, typically about 0.01 to 1.0 M Na ion concentration (or other salts) at pH 7.0 to 8.3, and the temperature is typically at least about 30xc2x0 C. Stringent conditions can also be achieved with the addition of destabilizing agents such as formamide. In general, a signal to noise ratio of 2xc3x97 (or higher) than that observed for an unrelated probe in the particular hybridization assay indicates detection of a specific hybridization. Nucleic acids that do not hybridize to each other under stringent conditions are still substantially similar if the proteins that they encode are substantially similar. This occurs, e.g., when a copy of a nucleic acid is created using the maximum codon degeneracy permitted by the genetic code.
The following are examples of sets of hybridization/wash conditions that may be used to identify homologous nucleotide sequences that are substantially similar to reference nucleotide sequences of the present invention: a test sequence that hybridizes to the reference nucleotide sequence in 7% sodium dodecyl sulfate (SDS), 0.5 M NaPO4, 1 mM EDTA at 50xc2x0 C. with washing in 2xc3x97SSC, 0.1% SDS at 50xc2x0 C., more desirably in 7% sodium dodecyl sulfate (SDS), 0.5 M NaPO4, 1 mM EDTA at 50xc2x0 C. with washing in 1xc3x97SSC, 0.1% SDS at 50xc2x0 C., more desirably still in 7% sodium dodecyl sulfate (SDS), 0.5 M NaPO4, 1 mM EDTA at 50xc2x0 C. with washing in 0.5xc3x97SSC, 0.1% SDS at 50xc2x0 C., preferably in 7% sodium dodecyl sulfate (SDS), 0.5 M NaPO4, 1 mM EDTA at 50xc2x0 C. with washing in 0.1xc3x97SSC, 0.1% SDS at 50xc2x0 C., more preferably in 7% sodium dodecyl sulfate (SDS), 0.5 M NaPO4, 1 mM EDTA at 50xc2x0 C. with washing in 0.1xc3x97SSC, 0.1% SDS at 65xc2x0 C. The polynucleotide of the invention that hybridizes under the above conditions preferably comprises at least 80 base pairs, more preferably at least 50 base pairs and particularly at least 21, and more particularly 18 base pairs. Preferred homologs of use in the invention include nucleic acid molecules that encode an amino acid sequence that is at least 45% identical to SEQ ID NO:2, 6 or 8 as measured, using the parameters described below, wherein the amino acid sequence encoded by the homolog has trichothecene resistance activity, e.g. 3-O-acetyltransferase activity.
The term xe2x80x9csubstantially similarxe2x80x9d, when used herein with respect to a protein, means a protein corresponding to a reference protein, wherein the protein has substantially the same structure and function as the reference protein, e.g. where only changes in amino acids sequence not affecting the polypeptide function occur. When used for a protein or an amino acid sequence the percentage of identity between the substantially similar and the reference protein or amino acid sequence desirably is at least 45% identity, more desirably at least 65%, more desirably at least 75%, preferably at least 85%, more preferably at least 90%, still more preferably at least 95%, yet still more preferably at least 99%, using default BLAST analysis parameters and as described in more detail below.
Preferred homologs of the polypeptide of use in the invention comprise those having amino acid sequences that are at least 45% identical to SEQ ID NO:2, 6 or 8, wherein the amino acid sequence encoded by the homolog has trichothecene resistance activity, e.g. 3-O-acetyl transferase activity.
Optimal alignment of nucleic acid or protein sequences for comparison can be conducted as described above and, e.g., by the local homology algorithm of Smith and Waterman, Adv. Appl. Math. 2: 482 (1981), by the homology alignment algorithm of Needleman and Wunsch, J. Mol. Biol. 48: 443 (1970), by the search for similarity method of Pearson and Lipman, Proc. Nat""l. Acad. Sci. USA 85: 2444 (1988), by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wis.), or by visual inspection (see generally, Ausubel et al., infra).
One example of an algorithm that is suitable for determining percent sequence identity and sequence similarity is the BLAST algorithm, which is described in Altschul et al., J. Mol. Biol. 215: 403-410 (1990). Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information. This algorithm involves first identifying high scoring sequence pairs (HSPs) by identifying short words of length W in the query sequence, which either match or satisfy some positive-valued threshold score T when aligned with a word of the same length in a database sequence. T is referred to as the neighborhood word score threshold (Altschul et al., 1990). These initial neighborhood word hits act as seeds for initiating searches to find longer HSPs containing them. The word hits are then extended in both directions along each sequence for as far as the cumulative alignment score can be increased. Cumulative scores are calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always greater than 0) and N (penalty score for mismatching residues; always less than 0). For amino acid sequences, a scoring matrix is used to calculate the cumulative score. Extension of the word hits in each direction are halted when the cumulative alignment score falls off by the quantity X from its maximum achieved value, the cumulative score goes to zero or below due to the accumulation of one or more negative-scoring residue alignments, or the end of either sequence is reached. The BLAST algorithm parameters W, T, and X determine the sensitivity and speed of the alignment. The BLASTN program (for nucleotide sequences) uses as defaults a wordlength (W) of 11, an expectation (E) of 10, a cutoff of 100, M=5, N=xe2x88x924, and a comparison of both strands. For amino acid sequences, the BLASTP program uses as defaults a wordlength (W) of 3, an expectation (E) of 10, and the BLOSUM62 scoring matrix (see Henikoff and Henikoff, Proc. Natl. Acad. Sci. USA 89: 10915 (1989)).
In addition to calculating percent sequence identity, the BLAST algorithm also performs a statistical analysis of the similarity between two sequences (see, e.g., Karlin and Altschul, Proc. Nat""l. Acad. Sci. USA 90: 5873-5787 (1993)). One measure of similarity provided by the BLAST algorithm is the smallest sum probability (P(N)), which provides an indication of the probability by which a match between two nucleotide or amino acid sequences would occur by chance. For example, a test nucleic acid sequence is considered similar to a reference sequence if the smallest sum probability in a comparison of the test nucleic acid sequence to the reference nucleic acid sequence is less than about 0.1, more preferably less than about 0.01, and most preferably less than about 0.001.
A further indication that two nucleic acid sequences or proteins are substantially similar is that the protein encoded by the first nucleic acid is immunologically cross reactive with, or specifically binds to, the protein encoded by the second nucleic acid. Thus, a protein is typically substantially similar to a second protein, for example, where the two proteins differ only by conservative substitutions.
The phrase xe2x80x9cspecifically (or selectively) binds to an antibody,xe2x80x9d or xe2x80x9cspecifically (or selectively) immunoreactive with,xe2x80x9d when referring to a protein or peptide, refers to a binding reaction which is determinative of the presence of the protein in the presence of a heterogeneous population of proteins and other biologics. Thus, under designated immunoassay conditions, the specified antibodies bind to a particular protein and do not bind in a significant amount to other proteins present in the sample. Specific binding to an antibody under such conditions may require an antibody that is selected for its specificity for a particular protein. For example, antibodies raised to the protein with the amino acid sequence encoded by any of the nucleic acid sequences of the invention can be selected to obtain antibodies specifically immunoreactive with that protein and not with other proteins except for polymorphic variants. A variety of immunoassay formats may be used to select antibodies specifically immunoreactive with a particular protein. For example, solid-phase ELISA immunoassays, Western blots, or immunohistochemistry are routinely used to select monoclonal antibodies specifically immunoreactive with a protein. See Harlow and Lane (1988) Antibodies, A Laboratory Manual, Cold Spring Harbor Publications, New York xe2x80x9cHarlow and Lanexe2x80x9d), for a description of immunoassay formats and conditions that can be used to determine specific immunoreactivity. Typically a specific or selective reaction will be at least twice background signal or noise and more typically more than 10 to 100 times background.
xe2x80x9cConservatively modified variationsxe2x80x9d of a particular nucleic acid sequence refers to those nucleic acid sequences that encode identical or essentially identical amino acid sequences, or where the nucleic acid sequence does not encode an amino acid sequence, to essentially identical sequences. Because of the degeneracy of the genetic code, a large number of functionally identical nucleic acids encode any given polypeptide. For instance the codons CGT, CGC, CGA, CGG, AGA, and AGG all encode the amino acid arginine. Thus, at every position where an arginine is specified by a codon, the codon can be altered to any of the corresponding codons described without altering the encoded protein. Such nucleic acid variations are xe2x80x9csilent variationsxe2x80x9d which are one species of xe2x80x9cconservatively modified variations.xe2x80x9d Every nucleic acid sequence described herein which encodes a protein also describes every possible silent variation, except where otherwise noted. One of skill will recognize that each codon in a nucleic acid (except ATG, which is ordinarily the only codon for methionine) can be modified to yield a functionally identical molecule by standard techniques. Accordingly, each xe2x80x9csilent variationxe2x80x9d of a nucleic acid which encodes a protein is implicit in each described sequence.
Furthermore, one of skill will recognize that individual substitutions deletions or additions that alter, add or delete a single amino acid or a small percentage of amino acids (typically less than 5%, more typically less than 1%) in an encoded sequence are xe2x80x9cconservatively modified variations,xe2x80x9d where the alterations result in the substitution of an amino acid with a chemically similar amino acid. Conservative substitution tables providing functionally similar amino acids are well known in the art. The following five groups each contain amino acids that are conservative substitutions for one another: Aliphatic: Glycine (G), Alanine (A), Valine (V), Leucine (L), Isoleucine (I); Aromatic: Phenylalanine (F), Tyrosine (Y), Tryptophan (W); Sulfur-containing: Methionine (M), Cysteine (C); Basic: Arginine (R), Lysine (K), Histidine (H); Acidic: Aspartic acid (D), Glutamic acid (E), Asparagine (N), Glutamine (Q). See also, Creighton (1984) Proteins, W. H. Freeman and Company. In addition, individual substitutions, deletions or additions which alter, add or delete a single amino acid or a small percentage of amino acids in an encoded sequence are also xe2x80x9cconservatively modified variations.xe2x80x9d
A xe2x80x9csubsequencexe2x80x9d refers to a sequence of nucleic acids or amino acids that comprise a part of a longer sequence of nucleic acids or amino acids (e.g., protein) respectively.
Nucleic acids are xe2x80x9celongatedxe2x80x9d when additional nucleotides (or other analogous molecules) are incorporated into the nucleic acid. Most commonly, this is performed with a polymerase (e.g., a DNA polymerase), e.g., a polymerase which adds sequences at the 3xe2x80x2 terminus of the nucleic acid.
Two nucleic acids are xe2x80x9crecombinedxe2x80x9d when sequences from each of the two nucleic acids are combined in a progeny nucleic acid. Two sequences are xe2x80x9cdirectlyxe2x80x9d recombined when both of the nucleic acids are substrates for recombination. Two sequences are xe2x80x9cindirectly recombinedxe2x80x9d when the sequences are recombined using an intermediate such as a cross-over oligonucleotide. For indirect recombination, no more than one of the sequences is an actual substrate for recombination, and in some cases, neither sequence is a substrate for recombination.
A xe2x80x9cspecific binding affinityxe2x80x9d between two molecules, for example, a ligand and a receptor, means a preferential binding of one molecule for another in a mixture of molecules. The binding of the molecules can be considered specific if the binding affinity is about 1xc3x97104 Mxe2x88x921 to about 1xc3x97106 Mxe2x88x921 or greater.
Substrate: a substrate is the molecule that an enzyme naturally recognizes and converts to a product in the biochemical pathway in which the enzyme naturally carries out its function, or is a modified version of the molecule, which is also recognized by the enzyme and is converted by the enzyme to a product in an enzymatic reaction similar to the naturally-ocurring reaction.
Transformation: a process for introducing heterologous DNA into a cell, tissue, or insect. Transformed cells, tissues, or insects are understood to encompass not only the end product of a transformation process, but also transgenic progeny thereof.
xe2x80x9cTransformed,xe2x80x9d xe2x80x9ctransgenic,xe2x80x9d and xe2x80x9crecombinantxe2x80x9d refer to a host organism such as a bacterium or a plant into which a heterologous nucleic acid molecule has been introduced. The nucleic acid molecule can be stably integrated into the genome of the host or the nucleic acid molecule can also be present as an extrachromosomal molecule. Such an extrachromosomal molecule can be auto-replicating. Transformed cells, tissues, or plants are understood to encompass not only the end product of a transformation process, but also transgenic progeny thereof. A xe2x80x9cnon-transformed,xe2x80x9d xe2x80x9cnon-transgenic,xe2x80x9d or xe2x80x9cnon-recombinantxe2x80x9d host refers to a wild-type organism, e.g., a bacterium or plant, which does not contain the heterologous nucleic acid molecule.
It is an object of the invention to provide a plant cell or cells comprising a heterologous polynucleotide encoding a gene product that is expressed in the plant cell wherein the gene product comprises trichothecene resistance activity.
Another object of the invention is to provide a plant comprising the above described plant cell wherein the plant is resistant to a trichothecene.
Another object of the invention is to provide a plant that is resistant to a trichothecene where the trichothecene comprises a C-3 hydroxyl group.
Another object of the invention is to provide a plant wherein the gene product is a 3-O-acetyltransferase.
Another object of the invention is to provide a plant of the invention wherein the heterologous polynucleotide is substantially similar to the nucleic acid sequence of SEQ ID NOs:1, 5 or 7.
Another object of the invention is to provide a plant of the invention wherein the heterologous polynucleotide comprises the nucleic acid sequence of SEQ ID NO:1, 5 or 7 or homologs thereof.
Another object of the invention is to provide a plant wherein the gene product is a polypeptide comprising a sequence substantially similar to SEQ ID NO:2, 6 or 8.
Another object of the invention is to provide a plant wherein the heterologous polynucleotide comprises the nucleic acid sequence of SEQ ID NO:1, 5 or 7.
Another object of the invention is to provide a plant comprising a heterologous polynucleotide, which comprises a consecutive 18 base pair portion identical in sequence to a consecutive 18 base pair portion set forth in SEQ ID NO:1, 5 or 7.
Another object of the invention is to provide a plant resistant to a trichothecene selected from the group consisting T-2 toxin, HT-2 toxin, isotrichodermol, 4,15-diacetoxyscirpenol (hereinafter xe2x80x9cDASxe2x80x9d), 3-deacetylcalonectrin, 3,15-dideacetylcalonectrin, scirpentriol, neosolaniol; type B: 15-acetyldeoxynivalenol, nivalenol, 4-acetylnivalenol (fusarenone-X), 4,15-diacetylnivalenol, 4,7,15-acetylnivalenol, and DON.
Another object of the invention is to provide a plant resistant to DAS or DON.
Another object of the invention is to provide a seed of any of the plants of the invention.
Another object of the invention is to provide anyone of the above-described plants wherein the plant is a wheat, maize, barley or rice plant.
Another object of the invention is to provide a plant that is resistant to a fungus that produces a trichothecene comprising a C-3 hydroxyl group.
Another object of the invention is to provide a plant that is resistant to Fusarium, Trichothecium or Myrothecium.
Another object of the invention is to provide a plant that is resistant to Fusarium, in particular but not limited to Fusarium graminearum, Fusarium culmorum, Fusarium sporotrichioides, Fusarium poae, Fusarium sambucinum, Fusarium equiseti, Fusarium acuminatum, Fusarium lateritium, and Fusarium pseudograminearum. 
Another object of the invention is to provide a plant that is resistant to Fusarium graminearum. 
Another object of the invention is to provide a plant of the invention as described above wherein the heterologous polynucleotide is a microbial polynucleotide.
Another object of the invention is to provide a plant of the invention as described above wherein the microbial polynucleotide is a yeast or fungal polynucleotide.
Another object of the invention is to provide a plant of the invention as described above wherein the fungal polynucleotide is a Fusarium polynucleotide.
Another object of the invention is to provide a plant of the invention as described above wherein the Fusarium polynucleotide is a Fusarium graminearum or Fusarium sporotrichioides polynucleotide.
Another object of the invention is to provide a plant as described above wherein the plant is resistant to a fungus that produces a trichothecene.
Another object of the invention is to provide a plant as described above wherein the plant is resistant to a fungus that produces a trichothecene comprising a C-3 hydroxyl group.
Another object of the invention is to provide a method for producing a trichothecene resistant plant comprising the steps of:
a) transforming a plant cell with a heterologous gene encoding a gene product, wherein the gene product increases resistance to a trichothecene; and
b) expressing the gene product at a biologically significant level.
c) regenerating the plant cell into a plant; and
d) selecting a plant having increased resistance to a trichothecene.
Another object of the invention is to provide a method as described above further comprising the step of selecting a plant on which there is reduced growth of a fungus where the fungus produces a trichothecene.
Another object of the invention is to provide a method as described above wherein the fungus is of the genera Fusarium.
Another object of the invention is to provide a trichothecene resistant plant obtained according to the above-described methods.
Another object of the invention is to provide a seed produced by selfing or outcrossing a plant of the invention as described above, wherein a plant grown from the seed has an increased resistance to trichothecene.
Another object of the invention is to provide a method of preventing mycotoxin crop contamination comprising growing a plant of the invention as described above, wherein the plant is a crop plant.
Another object of the invention is to provide a method of preventing fungal growth on a crop, comprising growing a plant of the invention as described above, wherein the plant is a crop plant.
Another object of the invention is to provide a method of selecting transformed host cells, the method comprising: transforming a host cell with a nucleic acid construct encoding a trichothecene 3-O-acetyltransferase, and growing the transformed host cell in the presence of a trichothecene selective agent.
Another object of the invention is to provide a method of selecting transformed host cells wherein the host cells are plant cells, or microbial cells, particularly where the microbial cells are fungal cells.
Another object of the invention is to provide a method of selecting transformed host cells as described above where the host cell is further transformed with a second polynucleotide of interest.
Another object of the invention is to provide a method of selecting transformed host cells wherein in the trichothecene is selected from the group the group consisting T-2 toxin, HT-2 toxin, isotrichodermol, DAS, 3-deacetylcalonectrin, 3,15-dideacetylcalonectrin, scirpentriol, neosolaniol; type B: 15-acetyldeoxynivalenol, nivalenol, 4-acetylnivalenol (fusarenone-X), 4,15-diacetylnivalenol, 4,7,15-acetylnivalenol, and DON.
Description of the Sequences:
SEQ ID NO:1 is a cDNA sequence from Fusarium sporotrichioides encoding a polypeptide of the invention having trichothecene resistance activity.
SEQ ID NO:2 is the polypeptide having trichothecene resistance activity encoded by SEQ ID NO: 1.
SEQ ID NO: 3 is a DNA primer.
SEQ ID NO 4: is a DNA primer.
SEQ ID NO: 5 is a DNA sequence from Fusarium graminearum encoding a polypeptide of the invention having trichothecene resistance activity.
SEQ ID NO: 6 is the polypeptide having trichothecene resistance activity encoded by SEQ ID NO:5.
SEQ ID NO. 7 is a DNA sequence from Saccharomyces cerevisiae encoding a polypeptide of the invention having trichothecene resistance activity.
SEQ ID NO. 8 is the polypeptide having trichothecene resistance activity encoded by SEQ ID NO:7.
SEQ ID NO. 9 is the DNA sequence of pCIB9818.
SEQ ID NO. 10 is the DNA sequence of pAgroTRIr.
SEQ ID NO. 11 is the DNA sequence of pNOV1704.